Photosensitive laminate structures have been used for many years in imaging surfaces of objects. A variety of photosensitive resins have been formulated in a variety of useful layers in these laminate structures. Electromagnetic radiation such as UV or light has been commonly used to imagewise expose such laminates and form an image in the laminate structure. The images can be then transferred to a surface for selective surface modification.
Ichimura, U.S. Pat. Nos. 4,272,620 and 4,564,580 discloses a photosensitive stilbazolium material comprising a styrylpyridinium group in a photosensitive resin. Such a material is disclosed for use in a layered structure. Namiki et al., U.S. Pat. No. 4,268,601 disclose a layered structure comprising a transparent support layer, a polyvinyl alcohol layer, a photosensitive resin composition and optionally an adhesive layer that can be used to adhere the material to a substrate. Goto et al., U.S. Pat. No. 4,430,416 disclose a transfer element for sandblasted carving comprising in order; a flexible substrate, a strippable intermediate resin layer having pressure sensitive properties and a photosensitive resin layer. Christensen et al., U.S. Pat. No. 4,530,896 disclose a light sensitive laminate comprising a support layer, a light sensitive photoresist layer and an intermediate protection layer comprising a light transmitting material. VanIseghem, U.S. Pat. No. 4,764,449 discloses a photoresist laminate comprising an adhesive layer, a membrane support layer and a resist layer which can be used in etching the surface of an article with a pattern. Suzuki et al., U.S. Pat. Nos. 5,427,890, 5,518,857 and 5,629,132 disclose a photosensitive laminate film useful in making an imaged mask comprising a substrate layer, a peelable image mask protection layer and a photosensitive layer. Suzuki et al. claim a non-photosensitive image mask protection layer that can be made from a peelable non-photosensitive water insoluble material such as polyvinyl alcohol derivatives, polyvinyl butyral, ethyl cellulose, cellulose acetate, cellulose nitrate and others. The image mask layer contains no exposed or unexposed photosensitive material and is formulated to protect and transfer the imaged layer to a surface. Suzuki et al. emphasize a choice of non-photosensitive materials that renders the image mask protection layer weakly adhered to the supporting sheet so it can be easily peeled.
Birkholm, U.S. Pat. No. 5,260,173 teaches a process for forming an integral membrane in a photosensitive laminate. The Birkholm structure comprises a support and a single photoimageable layer. An integral membrane or layer is made in the single photosensitive layer by exposing the photoresist with a proper amount of electromagnetic radiation for a controlled period of time to form a thin controllable integral membrane layer in the imageable photoresist while leaving the major part of the imageable layer unexposed for later imaging. The integral membrane, during processing including exposure and wash out, remains intact and greatly enhances the amount of detail available for transfer in the imagewise exposed portion of the photoresist layer. In Birkholm FIGS. 1 through 7 show several operating modes. In a first mode (see FIG. 3), after imaging, the integral membrane is formed by back exposing the unexposed areas without an image transfer means. In a next mode (see FIG. 7), the two layer structure comprising a support and a photoresist layer is exposed by radiation directed substantially normal to the surface of the resist layer for a controlled period of time to produce, on the surface of the resist layer, a thin integral membrane. In this mode the membrane is formed on the exterior of the resist, opposite the film carrier. In a last mode of operation (see claim 8) Birkholm suggests exposing the photosensitive laminate to radiation substantially normal to the substrate side for controlled period of time to produce a controlled integral membrane that is formed in the photosensitive layer at the interface between the substrate and the photosensitive layer. In these modes the membrane is formed in the interior of the structure. In the Birkholm et al. options, the integral membrane is formed from a single layer of photosensitive material formed on the substrate by controlled exposure to actinic radiation. For this technology to be successful, the exposure of the peelable layer must be done carefully. Lack of care in the exposure and image development can result in lack of control of layer dimensions, (i.e.) a thick or a thin layer. These variations can result in difficult processing and inconsistent results.